Test Bank for Molecular Cell Biology 9th Edition by
Harvey Lodish.
8. Which of the following is a negatively charged amino acid?
a. alanine
b. aspartate
c. glutamine
d. histidine
b
Which of the following is/are a hydrophilic amino acid?
a. aspartate
b. serine
c. tryptophan
d. aspartate and serine
d
Adenosine is a:
a. component of RNA.
b. nucleoside.
c. pyrimidine.
d. a and b
d
Which of the following is a monosaccharide?
a. fructose
b. galactose
c. glucose
d. all of the above
d
. Based on what you know about hydrophobic interactions, which of the following is/are composed of
a bilayer?
a. a cell's membrane
b. spontaneously aggregated phospholipids surrounding an aqueous interior
c. lipid vesicles that have budded off the cell's membrane
d. all of the above
d
You discover that you suffer from a deficiency in the amino acid tryptophan. At the pharmacy, you
find both d-tryptophan and l-tryptophan supplements. Which do you purchase? Why?
,You should choose l-tryptophan. All amino acids can exist as one of two stereoisomers (d or l) because
of asymmetry around the α carbon. Proteins consist of the l form of amino acids, and as these
stereoisomers possess distinct biological properties and are not readily interconverted, you should
choose the form that is normally utilized by cells.
Cysteine often plays an important role in stabilizing protein structure. Explain how this works.
: Two adjacent sulfhydryl (SH) groups can oxidize to form a covalent disulfide (S-S) bond. Disulfide bonds
can stabilize the structure of folded peptides or sometimes link two separate peptide chains together.
Triacylglycerol and cholesterol esters are nonpolar; in contrast, phospholipids are amphipathic
molecules. Biomembranes are based on phospholipids rather than on triacylglycerols. Why?
Biomembranes are based on phospholipids rather than on triacylglycerols because phospholipids as
amphipathic molecules can form planar lipid bilayers, whereas the nonamphipathic nonpolar
triacylglycerols cannot. Their amphipathic property, the presence of a polar and nonpolar domain at
opposite ends of the same molecule, allows phospholipids to form hydrophilic associations with water
at the same time as forming hydrophobic associations with each other through their hydrophobic tails.
Triacylglycerols are strictly hydrophobic in nature and hence in an aqueous environment tend to
associate with one another to form lipid droplets. This minimizes the contact of triacylglycerol with
water. Recall the old adage: oil and water do not mix.
A nucleotide can vary in _____.
a. the base
b. the sugar
c. the phosphate group
d. the sugar and the base
d
Which of the following is NOT one of the ways RNA differs from DNA?
a. Ribonucleotides have a hydroxyl group on the 2 carbon of their sugar subunit.
b. Ribonucleotides can have enzymatic activity.
c. Ribonucleotides contain a phosphate group.
d. Ribonucleotides can contain the base uracil.
c
What is the major structural difference between starch and cellulose?
a. the types of monosaccharide subunits in the molecules
b. the amount of branching that occurs in the molecule
c. that humans can only ingest starch
d. the type of glycosidic linkages in the molecule
d
How do phospholipids interact with water molecules?
a. The polar heads interact with water; the nonpolar tails do not.
b. Phospholipids don't interact with water because water is polar and lipids are nonpolar.
,c. The polar heads avoid water; the nonpolar tails attract water (because water is polar and opposites
attract).
d. Phospholipids dissolve in water.
a
Which of the following is the BEST explanation for why vegetable oil is a liquid at room temperature
while animal fats are solid?
a. Vegetable oil has fewer double bonds than animal fats.
b. Animal fats have no amphipathic character.
c. Vegetable oil has longer fatty-acid tails than do animal fats.
d. Vegetable oil has more double bonds than do animal fats.
a
A 1-mL solution of 0.05 M H2SO4 is diluted to 100 mL at 25°C. What is the pH of the resulting solution?
a. 1
b. 2
c. 3
d. 4
c
An Archaea cell living in an abandoned mine is found to contain a very high concentration of protons.
It is likely that this cell:
a. has a high ph and is acidic.
b. has a high ph and is alkaline.
c. has low ph and is acidic.
d. has a low pH and is alkaline.
c
A 1-mL solution of 0.1 M NaOH is diluted to 1 L at 25°C. What is the pH of the resulting solution?
a. 1
b. 7
c. 10
d. 13
c
The pKa of the weak base NH3 is 9.25. When present in lysosomes, a subcellular organelle—
ammonia—is almost totally protonated. Which of the pH values listed below is most likely to be that
of the lysosome lumen?
a. 1
b. 5
c. 8
d. 14
b
, If the equilibrium constant for the reaction A ® B is 0.5 and the initial concentration of A is 25 mM and
of B is 12.5 mM, then the reaction:
a. will proceed in the direction it is written, producing a net increase in the concentration of B.
b. will produce energy, which can be used to drive ATP synthesis.
c. will proceed in the reverse direction, producing a net increase in the concentration of A.
d. is at equilibrium.
d
For the binding reaction A + B -> AB, the dissociation constant is equal to:
a. [AB]/([A] + [B]).
b. ([A] + [B])/[AB].
c. Keq
d. The first and third answers are correct.
b
. What is the effect of an enzyme on the end equilibrium concentration of reactants and products?
An enzyme has no effect on the end equilibrium concentration of reactants and products.
The enzyme alcohol dehydrogenase is capable of catalyzing the oxidation of a number of different
substances, including ethanol, ethylene glycol, and methanol, to an aldehyde. The metabolic products
of both ethylene glycol and methanol are highly toxic to humans. A standard medical treatment for
prevention of ethylene glycol or methanol poisoning is the administration of a dose of ethanol. Why is
this treatment effective?
The ethanol-like ethylene glycol and methanol are capable of binding to the enzyme, alcohol
dehydrogenase, and competing with its other substrates. A sufficient dosage of ethanol can out-
compete the other substrates, and hence the ethylene glycol and methanol are not metabolized to toxic
products. Gradually the ethylene glycol or methanol will be excreted from the body.
How do cells maintain a relatively constant pH despite the fact that many metabolic processes
produce acids?
All cells contain buffers such as phosphate ions that can absorb or release protons or hydroxyl ions to
stabilize pH changes near neutral pH.
In a biochemical reaction in which DH < 0 and DS > 0:
a. the reaction is spontaneous.
b. the reaction is endothermic.
c. the reaction is endergonic.
d. DG is positive.
a
. In the reaction NAD+ + H+ + 2e− ® NADH, NAD+ becomes:
a. dehydrated.
b. hydrolyzed.
Harvey Lodish.
8. Which of the following is a negatively charged amino acid?
a. alanine
b. aspartate
c. glutamine
d. histidine
b
Which of the following is/are a hydrophilic amino acid?
a. aspartate
b. serine
c. tryptophan
d. aspartate and serine
d
Adenosine is a:
a. component of RNA.
b. nucleoside.
c. pyrimidine.
d. a and b
d
Which of the following is a monosaccharide?
a. fructose
b. galactose
c. glucose
d. all of the above
d
. Based on what you know about hydrophobic interactions, which of the following is/are composed of
a bilayer?
a. a cell's membrane
b. spontaneously aggregated phospholipids surrounding an aqueous interior
c. lipid vesicles that have budded off the cell's membrane
d. all of the above
d
You discover that you suffer from a deficiency in the amino acid tryptophan. At the pharmacy, you
find both d-tryptophan and l-tryptophan supplements. Which do you purchase? Why?
,You should choose l-tryptophan. All amino acids can exist as one of two stereoisomers (d or l) because
of asymmetry around the α carbon. Proteins consist of the l form of amino acids, and as these
stereoisomers possess distinct biological properties and are not readily interconverted, you should
choose the form that is normally utilized by cells.
Cysteine often plays an important role in stabilizing protein structure. Explain how this works.
: Two adjacent sulfhydryl (SH) groups can oxidize to form a covalent disulfide (S-S) bond. Disulfide bonds
can stabilize the structure of folded peptides or sometimes link two separate peptide chains together.
Triacylglycerol and cholesterol esters are nonpolar; in contrast, phospholipids are amphipathic
molecules. Biomembranes are based on phospholipids rather than on triacylglycerols. Why?
Biomembranes are based on phospholipids rather than on triacylglycerols because phospholipids as
amphipathic molecules can form planar lipid bilayers, whereas the nonamphipathic nonpolar
triacylglycerols cannot. Their amphipathic property, the presence of a polar and nonpolar domain at
opposite ends of the same molecule, allows phospholipids to form hydrophilic associations with water
at the same time as forming hydrophobic associations with each other through their hydrophobic tails.
Triacylglycerols are strictly hydrophobic in nature and hence in an aqueous environment tend to
associate with one another to form lipid droplets. This minimizes the contact of triacylglycerol with
water. Recall the old adage: oil and water do not mix.
A nucleotide can vary in _____.
a. the base
b. the sugar
c. the phosphate group
d. the sugar and the base
d
Which of the following is NOT one of the ways RNA differs from DNA?
a. Ribonucleotides have a hydroxyl group on the 2 carbon of their sugar subunit.
b. Ribonucleotides can have enzymatic activity.
c. Ribonucleotides contain a phosphate group.
d. Ribonucleotides can contain the base uracil.
c
What is the major structural difference between starch and cellulose?
a. the types of monosaccharide subunits in the molecules
b. the amount of branching that occurs in the molecule
c. that humans can only ingest starch
d. the type of glycosidic linkages in the molecule
d
How do phospholipids interact with water molecules?
a. The polar heads interact with water; the nonpolar tails do not.
b. Phospholipids don't interact with water because water is polar and lipids are nonpolar.
,c. The polar heads avoid water; the nonpolar tails attract water (because water is polar and opposites
attract).
d. Phospholipids dissolve in water.
a
Which of the following is the BEST explanation for why vegetable oil is a liquid at room temperature
while animal fats are solid?
a. Vegetable oil has fewer double bonds than animal fats.
b. Animal fats have no amphipathic character.
c. Vegetable oil has longer fatty-acid tails than do animal fats.
d. Vegetable oil has more double bonds than do animal fats.
a
A 1-mL solution of 0.05 M H2SO4 is diluted to 100 mL at 25°C. What is the pH of the resulting solution?
a. 1
b. 2
c. 3
d. 4
c
An Archaea cell living in an abandoned mine is found to contain a very high concentration of protons.
It is likely that this cell:
a. has a high ph and is acidic.
b. has a high ph and is alkaline.
c. has low ph and is acidic.
d. has a low pH and is alkaline.
c
A 1-mL solution of 0.1 M NaOH is diluted to 1 L at 25°C. What is the pH of the resulting solution?
a. 1
b. 7
c. 10
d. 13
c
The pKa of the weak base NH3 is 9.25. When present in lysosomes, a subcellular organelle—
ammonia—is almost totally protonated. Which of the pH values listed below is most likely to be that
of the lysosome lumen?
a. 1
b. 5
c. 8
d. 14
b
, If the equilibrium constant for the reaction A ® B is 0.5 and the initial concentration of A is 25 mM and
of B is 12.5 mM, then the reaction:
a. will proceed in the direction it is written, producing a net increase in the concentration of B.
b. will produce energy, which can be used to drive ATP synthesis.
c. will proceed in the reverse direction, producing a net increase in the concentration of A.
d. is at equilibrium.
d
For the binding reaction A + B -> AB, the dissociation constant is equal to:
a. [AB]/([A] + [B]).
b. ([A] + [B])/[AB].
c. Keq
d. The first and third answers are correct.
b
. What is the effect of an enzyme on the end equilibrium concentration of reactants and products?
An enzyme has no effect on the end equilibrium concentration of reactants and products.
The enzyme alcohol dehydrogenase is capable of catalyzing the oxidation of a number of different
substances, including ethanol, ethylene glycol, and methanol, to an aldehyde. The metabolic products
of both ethylene glycol and methanol are highly toxic to humans. A standard medical treatment for
prevention of ethylene glycol or methanol poisoning is the administration of a dose of ethanol. Why is
this treatment effective?
The ethanol-like ethylene glycol and methanol are capable of binding to the enzyme, alcohol
dehydrogenase, and competing with its other substrates. A sufficient dosage of ethanol can out-
compete the other substrates, and hence the ethylene glycol and methanol are not metabolized to toxic
products. Gradually the ethylene glycol or methanol will be excreted from the body.
How do cells maintain a relatively constant pH despite the fact that many metabolic processes
produce acids?
All cells contain buffers such as phosphate ions that can absorb or release protons or hydroxyl ions to
stabilize pH changes near neutral pH.
In a biochemical reaction in which DH < 0 and DS > 0:
a. the reaction is spontaneous.
b. the reaction is endothermic.
c. the reaction is endergonic.
d. DG is positive.
a
. In the reaction NAD+ + H+ + 2e− ® NADH, NAD+ becomes:
a. dehydrated.
b. hydrolyzed.
